Kinetics of the reactive sintering of kaolinite-aluminum hydroxide extrudate

The kinetics of the reactive sintering process of the extrudate made of a kaolinite and aluminum hydroxide mixture is investigated by means of stepwise isothermal dilatometry (SID) accompanied with XRD, SEM and other techniques. We find that the process can be divided into three stages in total, and the isothermal shrinkage data can be well-fitted according to Makipirtti-Meng equation: dY/dt = nk(T) Y(1 - Y)[(1 - Y)/Y](1/n), where Y is the fractional densification function. The apparent activation energy E-a values are obtained as 2972 +/- 461.kJ.mol(-1) for 950-1100 degreesC, 1056+/-74 kJ mol(-1) for 1200-1300 degreesC, and 792.7+/-17.0 kJ mol(-1) for 1300-1450 degreesC. The sintering shrinkage mechanisms in different temperature ranges are discussed, with reference to phase, pore and microstructure development. This study is helpful to control the microstructure and properties of the porous mullite-corundum ceramics. (C) 2002 Elsevier Science Ltd and Techna S.r.l. All rights reserved.